Simulation job length when there are no restart files

[SalvatoreDiGirolamo]

If the analysis asks for a file that is after the last restart file, SimFS launches a simulation that goes from the last restart file to the asked file, so it does not cover a full restart interval. This may be inefficient for analyses accessing that part of the simulation output: potentially, we get a resimulation for each asked file.

Note: a work around is to manually create a restart file (even a fake one) at the end of the simulation time. However, if there are no other restart files, an analysis interested in few files at the beginning of the simulation may still trigger a full resimulation.

Note: the prefetcher should fix this issue by creating longer simulation jobs able to mask the restart latency. We have two cases: (1) the simulation job will be long enough to reach the simulation end; (2) still multiple simulation jobs will be needed by the analysis will not notice that because the restart latency is overlapped.
TODO: double check that the prefetcher works well in this case.

[ruestefa]

Note: a work around is to manually create a restart file (even a fake one) at the end of the simulation time. However, if there are no other restart files, an analysis interested in few files at the beginning of the simulation may still trigger a full resimulation.

Reading this, I think the best solution for standard cases would be to just allow analysis tools to specify the output interval they are interested in. I guess pretty much all analyses not covering the full simulation period know the start and end timestep, so allowing them to specify that in the run script would solve this issue for these cases.

Tools covering the whold analysis period without being aware of its duration (e.g., looping over 'output/*') could fall back to the global analysis duration that is specified in the context (and may be enfoced by SimFS under the hood by aid of a fake restart file in the end).

No really new thoughts, but it cannot hurt to add them here. :-)